A backlight module (10) includes a flat cold cathode fluorescent lamp (CCFL) (30) having an output interface, and a light guiding plate (20). The output interface has a nano-material layer coated thereon. The light guiding plate includes an incidence interface (21), an emission interface (23), and a reflection interface (22), wherein the emission interface and the reflection interface respectively have nano-sized V-shaped grooves provided thereat. A pitch of the V-shaped grooves of the emission interface gradually increases from the incidence interface to a side of the light guiding plate distal from the incidence interface, and a pitch of the V-shaped grooves of the reflection interface gradually increases from the incidence interface to the side of the light guiding plate distal from the incidence interface.